The idea of transition curves was first presented by Pressel in 1854, and first
used in the construction of the Brenner Railway 1864-1867. Nowadays, the use
of transition curves in horizontal curves is common practice, both between a
circular curve and an adjacent straight, and between circular curves with
different radii. The transition curves increase the time span for changing lateral
acceleration perceived by the passengers, hence reducing lateral jerk.
However, there are still curves (designed or existing) without transition
curves. One of the reasons for omitting the transition curves may be that there is
no change of cant between two elements with different curvature and lateral jerk
is based on the assumptions of virtual transitions.
The concept of virtual transition is as follows. As long as both bogies of a
vehicle are on a straight track, the lateral accelerat